1. Field of the Invention
This invention relates generally to casters, and more particularly to casters having means for selectively locking the caster in a trailing (tracking) position, so that it does not swivel from that position, and alternately to lock both the swivel and the wheel, so the caster will neither swivel nor roll.
2. Description of the Prior Art
Casters having anti-shimmy features are known. An example is shown in U.S. Pat. No. 2,480,524 where a resilent arm 19 presses against a stationary shell 9 of the assembly to minimize shimmy of the caster as it rolls along a surface. U.S. Pat. No. 3,518,714 discloses a device for preventing swiveling of a caster when it leaves contact with the ground.
Other arrangements have been made to actually lock the caster swivel. An example of a spring loaded manually adjustable detent lock appears in U.S. Pat. No. 2,654,112. U.S. Pat. No. 3,636,586 discusses problems involved in combinations of swiveling and nonswiveling wheels on push carts and pull carts, and provides a caster in which there is a member for locking the swiveling of selected casters on a piece of equipment such as stretchers or other emergency hospital equipment. Swivel locking therein involves operating a lever about a horizontal axis. U.S. Pat. No. 3,974,542 provides a swivel lock which can be actuated by horizontal linear movement of a slide control lever.
Some patents disclosing simultaneous braking of the wheel and locking of the swivel are as follows: U.S. Pat. Nos 2,484,094; 2,494,696; 2,572,548; 2,707,794; 2,709,828; 3,239,873; and 3,571,842. The casters shown in these patents have various ways of locking the swivel and brake, and the last patent on the list uses a push button which can be pushed to lock the caster, and then pushed again, to release the caster. These patents lock the wheel and swivel simultaneously. However, there are many instances where it is desireable to be able to lock the caster from swiveling, without necessarily braking the wheel, but also to brake the wheel, if desired.
There are U.S. patents disclosing casters in which swivel locking can be achieved, independently of wheel locking, but both can be achieved, if desired. An example is U.S. Pat. No. 2,915,775 to Skupas. In that patent, position 61 for the lever 51 provides locking of both the swivel and the wheel. Position 63 of the lever provides locking of only the swivel. The position intermediate 61 and 63 frees both the swivel and wheel. The patent discloses four notches 23 in the stationary portion of the assembly, and which can be used to establish four swivel positions, ninety degrees from each other. The patent discloses varying the number of swivel lock positions, if desired. In this instance, as in some of the above mentioned patents, the lever is foot operated and pivots about a horizontal axis.
Another patent which discloses means for locking the wheel from rolling and horn from swiveling is U.S. Pat. No. 3,055,042. In this example, clockwise rotation of the member 86 about a vertical axis of swiveling of the caster, serves to lock both the wheel and the horn, simultaneously. If it desired to lock the horn for two front casters in a trailing position, spring-loaded detents 156 are provided and operable independently of the brake applying notched disk 86. There does not appear to be any single lever operable to alternately apply a swivel lock, or a combination of the swivel and wheel lock.
U.S. Pat. No. 3,388,419 discloses a caster in which a lever 50 operable about a horizontal axis can be used to lock against both rotation of the wheel and swiveling of the caster in one position, against swiveling only in another position, or permit both swiveling and wheel rotation in the third position. It employs a combination of levers and links to do this. Haussels U.S. Pat. No. 3,911,525 discloses another arrangement for either locking the swivel, or locking both the swivel and the wheel, and uses a longitudinally vertically movable shaft having alternate positions to achieve these alternate results, and a third position to permit both free swiveling and rolling. It discloses a centrally locatable caster with a "fixing pin" 1 for projecting into a foot of a hospital bed and having an adjusting bolt extending axially through the pin and movable axially by a central adjusting linkage for operation of the caster control.
In addition to the Haussels U.S. Pat. No. 3,911,525 mentioned above, there are other patents disclosing the use of centralized control for simultaneous operation of swivel or braking mechanisms on casters. For example, Shepherd Pat. No. 3,159,865 shows apparatus wherein lever and link mechanism operating on horizontal axis serve to operate a vertical plunger in a bed post to simultaneously brake both the swivel and wheel. The weight of the bed is used to apply the braking force.
U.S. Pat. Nos. 3,431,584 and 3,479,681 show casters which use separately operable levers to simultaneously operate swivel locks, or brake locks in caster assemblies. Here also it is necessary that the mechanisms be operable down through the center of the swivel axis of the casters. In the later of these two patents, the raising of locking lever 212 for the swivel lock will cause a pin to drop in one of the circularly spaced holes in the horn assembly, to provide the swivel locking effect. The above mentioned U.S. Pat. No. 3,055,042 suggests remote control of various casters on an apparatus but, does not provide the single-lever option of either locking the swivel or locking both the swivel and the wheel.
U.S. Pat. No. 3,142,086 discloses a centrally operable handle 22 for operating slide bars simultaneously engage the horns of four casters on a typewriter stand, to prevent swiveling of the casters, but still permits the wheels to roll.
U.S. Pat. No. 2,728,936 discloses a lever 176 for engaging a lug in a notch in a horn to prevent swiveling, and another lever 192 for squeezing the sides of the horn together against the sides of the wheel to provide braking action.
There might very well be additional prior art disclosing various types of caster swivel and braking mechanism. The above art is the most pertinent known to us. Yet it does not provide apparatus which is simple in construction, operable by a single lever pivoting about a vertical axis to facilitate remote operation from a single point on a hospital bed or other equipment to provide the three options of free wheeling and swiveling, free wheeling without swiveling, and the combination of swivel and wheel locking. The present invention is addressed to this remaining need.